If the arms of your fabric-covered chair or sofa look darker and feel colder than the rest of the chair fabric, it is patina from your hands. Highly admired on old wood but not on fabric.
Most of it can be removed with a simple cleaner. Put two or three drops of a clear dishwashing liquid, such as Ivory, in a shallow bowl of warm water. Use a fork to whip up suds.
Take a thin, white washcloth and put some of the suds on top of the chair or sofa arm. Blot, do not rub, the patina. Some fabrics can be destroyed by rubbing across the weave. Be gentle. Do not use this method on sensitive fabrics such as silk.
You should be able to see the washcloth get darker. That means that the cleaning process is working.
With each application, use a new spot on the washcloth. Let the chair or sofa fabric dry for a few hours, or overnight, before judging the results.
Cleaning leather is best left to professionals. However, if you have a small grease spot that is slightly darker than the rest of the leather, you can apply the same suds as for fabric but use mainly water.
Since there are many qualities of leather, it is best to not use a leather conditioner. Plain water is your best choice.
Some textiles that feel like leather are actually engineered or bonded “leather,” created by grinding leftover leather scraps into mulch, mixing it with polyurethane, then applying it to a fabric backing. One particular manufacturer lists the contents as 58 percent polyurethane, 25 percent polyester/cotton and 17 percent leather.
Unlike real leather, the color and texture are only skin deep — a very thin layer on top of the fabric backing. Any scratches will reveal the fabric back. It feels like real leather but is as close to real leather as a Presto Log is to real wood.
The very best solution is for a professional cleaner to take the chair or sofa from your home, bring it to the shop and do a thorough cleaning of all the fabric. Some companies can do quite a good job right in your home. It does cost more, but is probably a very good choice, especially if the furniture has been in your house for several years.